Multilayer coating systems are well known in the automotive coating industry. These coating systems comprise a pigmented basecoat and a clear topcoat. In U.S. Pat. No. 4,598,015 are described a number of basecoat-clearcoat systems, in which both the basecoat and the clearcoat are pigmented in order to be aesthetically pleasing as well as durable.
The U.S. Pat. No. 4,728,543 discloses a clear topcoat composition of a film-forming acrylic polymer having a plurality of cross-linkable functional groups, solvents, a cross-linking agent and microgel particles. But these systems do not meet all requirements of the automotive industry for the topcoat in terms of mechanical properties, more specifically in terms of solvent resistance and acid resistance.
An object of the present invention is to provide a multilayer coating system for the automotive coating industry which includes a topcoat which exhibits superior solvent resistance, acid resistance and hardness compared to the acrylic/melamine clearcoats of the Prior Art.